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Showing papers on "Lift-induced drag published in 1983"


Proceedings ArticleDOI
01 Jan 1983
TL;DR: In this paper, the passive shock wave/boundary layer interaction control for reducing the drag in 12 percent thick circular arc and 14 percent thick supercritical airfoils was conducted in a 3 in. x 15.4 in. transonic wind tunnel at transonic Mach numbers.
Abstract: An investigation of the passive shock wave/boundary layer interaction control for reducing the drag in 12 percent thick circular arc and 14 percent thick supercritical airfoils was conducted in a 3 in. x 15.4 in. transonic wind tunnel at transonic Mach numbers. A porous surface with a cavity beneath it was positioned on the area of the airfoils, mounted on the test section bottom wall, where the shock wave occurs. The static pressure distributions over the airfoil, the wake impact pressure data for determining the profile drag, and the Schlieren photographs for porous surface airfoils are presented and compared with the results for solid surface airfoils. With the porous surface the normal shock wave for solid surface was changed to a lambda shock wave system, and the wake impact pressure data indicated an appreciable drag reduction for both airfoils with the porous surface at transonic speeds while causing little or no loss of lift. The effect of porosity and cavity size is investigated and off-design performance is discussed.

107 citations


Journal ArticleDOI
TL;DR: A model of the mechanics of gliding without loss of altitude (horizontal gliding) is developed and glide distances for given initial and final velocities are significantly increased in the influence of the ground effect over out of ground effect values.

54 citations


Journal ArticleDOI
TL;DR: In this article, the relative efficiency of canard, tandem, and aft-tailed aircraft configurations through analysis of an elementary lifting system was examined, and two general solutions emerged for minimum induced drag as a function of the geometry and the division of lift between the surfaces of such a system - one for fixed span and the other for fixed weight.
Abstract: This paper examines the relative efficiency of canard, tandem, and aft-tailed aircraft configurations through analysis of an elementary lifting system. Stability and trim requirements are imposed upon the system and its C sub L(max), drag, and structural weight are studied as its geometry varies over a wide range of possible configurations. During the course of the analysis, two general solutions emerge for minimum induced drag as a function of the geometry and the division of lift between the surfaces of such a system - one for fixed span and the other for fixed weight. The conclusion is that the pre-eminence of the conventional aft-tailed configuration has a sound fundamental basis, but that there may be some room for improvement.

26 citations


Journal ArticleDOI
TL;DR: In this article, the effects of various boat-tailed afterbodies on the drag of a long body of square section at zero incidence were measured in a wind tunnel at low Mach number.

25 citations


01 Apr 1983
TL;DR: In this article, the primary effects of Reynolds number on two dimensional airfoil characteristics are discussed and the universal scaling laws and easily implemented methods are developed to account for Reynolds number effects in helicopter rotor analyses.
Abstract: The primary effects of Reynolds number on two dimensional airfoil characteristics are discussed. Results from an extensive literature search reveal the manner in which the minimum drag and maximum lift are affected by the Reynolds number. C sub d sub min and C sub l sub max are plotted versus Reynolds number for airfoils of various thickness and camber. From the trends observed in the airfoil data, universal scaling laws and easily implemented methods are developed to account for Reynolds number effects in helicopter rotor analyses.

25 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of two blown jets on the aerodynamic characteristics of a 20°7o-thick, 8.5 % -cambered elliptical airfoil are described.
Abstract: Effects of two blown jets on the aerodynamic characteristics of a 20°7o-thick, 8.5 % -cambered elliptical airfoil are described. The jet slots are designed so that the jets are tangential to the blunt rear surface of the airfoil. Section lift, drag, and moment coefficients are given for the airfoil at 0-deg angle of attack for a freestream wind tunnel velocity of approximately 30 m/s (98-100 ft/s) and a Reynolds number of 9.5 x 105. Two jets are found to be more effective in producing lift than a single jet at the same total blowing momentum coefficient.

18 citations


Proceedings ArticleDOI
01 Jul 1983
TL;DR: In this article, the effect of shoulder radiusing and circumferentially grooving the afterbodies of bluff bodies to reduce the base drag at low speeds was discussed, and it was shown that increasing the shoulder radius to 2.75 body diameters can reduce the drag levels to those of a streamline body having 67 percent greater fineness ratio.
Abstract: The effect of shoulder radiusing and circumferentially grooving the afterbodies of bluff bodies to reduce the base drag at low speeds is discussed. Shoulder radii as large as 2.75 body diameters are examined. Reynolds number based on body diameter varied from 20,000 to 200,000. Results indicate that increasing the shoulder radius to 2.75 body diameters can reduce the drag levels to those of a streamline body having 67 percent greater fineness ratio. For zero shoulder radius, circumferential grooves were found to be effective in reducing body drag for zero shoulder radius in both laminar and tripped flow. Circumferential grooves on the afterbody with a shoulder radius of one-half the body diameter were only effective in reducing drag for laminar flow.

18 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the possibility of using both a canard and tailplane for trimming and concluded that improvements of approximately 20% in lift-drag ratio are theoretically possible at high lift coefficients by the use of an additional trimming surface.
Abstract: The prospect of reducing the induced drag of an aircraft by using both a canard and tailplane for trimming is investigated and results are compared with those for conventional tail-aft and canard arrangements. It is concluded that improvements of approximately 20% in lift-drag ratio are theoretically possible at high lift coefficients by the use of an additional trimming surface.

12 citations


Journal ArticleDOI
TL;DR: The use of a combination of steady-state and dynamic test maneuvers has resulted in a drastic reduction in the amount of flight time required to obtain sufficient data for the determination of the zero lift drag, induced drag characteristics and drag increments due to aircraft configuration changes as mentioned in this paper.
Abstract: : Performance trials of the European combat aircraft TORNADO have concentrated on the systematic measurement of lift and drag polars. Such polars have been successfully measured by means of well-adapted test instrumentation, a data reduction system, and a high calibration standard of the aircraft and engines. The use of a certain combination of steady-state and dynamic test maneuvers has resulted in a drastic reduction in the amount of flight time required to obtain sufficient data for the determination of the zero lift drag, induced drag characteristics and drag increments due to aircraft configuration changes. Flight test results are presented which demonstrate the advantage of the test technique used and the high data quality achieved.

12 citations


Journal ArticleDOI
TL;DR: In this paper, an iterative method for calculating wall interference corrections to model lift and induced drag from simple flowfield measurements is presented, applied to low-speed solid-wall wind tunnels, where the only measurements required are wall static pressures.
Abstract: An iterative method for calculating wall interference corrections to model lift and induced drag from simple flowfield measurements is presented. The method is applied to low-speed solid-wall wind tunnels, where the only measurements required are wall static pressures. The procedure for the iterations is described and the criterion for convergence to unconfined flow is given. The advantages of this method are that it easily handles cases having strong viscous effects, models with running propellers, etc. The viability of the procedure is demonstrated in a low-speed wind tunnel test of a wing model. A comparison shows that the standard method of images undercorrects, in this particular case, by about 20-30%.

11 citations


Patent
27 Jan 1983
TL;DR: In this article, the vortex flow is disturbed in a deliberate manner in that additional bodies are arranged on the wing in the region where the vortices are created, and the rotation direction of which vortice is in each case in the opposite direction to that of the free vortex located at the same position along the span.
Abstract: In the case of a method for reducing the induced drag of a lift-generating wing (aerofoil) which causes free angles on the wing, the vortex flow is disturbed in a deliberate manner in that additional bodies are arranged on the wing in the region where the vortices are created. At the same time, artificial vortices are produced at discrete points on the wing with the aid of the additional bodies, the rotation direction of which vortices is in each case in the opposite direction to that of the free vortex located at the same position along the span. Their vortex intensities are in this case controlled such that they are at least approximately the same as that of the free vortex at the same point along the span. A device is used for carrying out the method, in the case of which device vortex generators in the form of flow apparatuses having an air throughput are arranged on the wing, which flow apparatuses in each case have a spin-generating, adjustable air-guidance system in their interior.

Proceedings ArticleDOI
01 Dec 1983
TL;DR: In this paper, a theoretical and experimental program in which a wing concept for supersonic maneuvering was developed and then demonstrated experimentally in a series of wind tunnel tests is described.
Abstract: A theoretical and experimental program in which a wing concept for supersonic maneuvering was developed and then demonstrated experimentally in a series of wind tunnel tests is described. For the typical fighter wing, the problem of obtaining efficient lift at supersonic maneuvering C sub 's occurs due to development of a strong crossflow shock, and boundary layer separation. A natural means of achieving efficient supersonic maneuvering is based on controlling the non-linear inviscid crossflow on the wing in a manner analogous to the supercritical aerodynamic methods developed for transonic speeds. The application of supercritical aerodynamics to supersonic speeds is carried out using Supercritical Conical Camber (SC3). This report provides an aerodynamic analysis of the effort, with emphasis on wing design using non-linear aerodynamics. The substantial experimental data base is described in three separate wind tunnel reports, while two of the computer programs used in the work are also described in a separate report. Based on the development program it appears that a controlled supercritical crossflow can be obtained reliably on fighter-type wing planforms, with an associated drag due to lift reduction of about 20% projected using this concept.

Journal ArticleDOI
R. Shedden1, S. P. Lin1
TL;DR: In this article, the authors measured the drag force acting on a circular cylinder fluctuating erratically in a viscous fluid with a laser-cantilever force transducer.
Abstract: The drag force acting on a circular cylinder fluctuating erratically in a viscous fluid is measured with a laser–cantilever force transducer. The experimental results compare very well with the theory.

Proceedings ArticleDOI
01 Jan 1983
TL;DR: In this article, a hinge-line setback was proposed for exploiting leading-edge suction in conjunction with vortex flaps to improve the overall thrust per unit flap area, which was tested on a 60-deg cropped delta wing model.
Abstract: Segmented vortex flaps were suggested as a means of delaying the vortex spill-over causing thrust loss over the outboard region of single-panel flaps. Also proposed was hinge-line setback for exploiting leading-edge suction in conjunction with vortex flaps to improve the overall thrust per unit flap area. These two concepts in combination were tested on a 60-deg cropped delta wing model. Significant improvement in flap efficiency was indicated by a reduction of the flap/wing area from 11.4% of single-panel flap to 6.3% of a two segment delta flap design, with no lift/drag penalty at lift coefficients between 0.5 and 0.7. The more efficient vortex flap arrangement of this study should benefit the performance attainable with flaps of given area on wings of moderate leading-edge sweep.

01 Jun 1983
TL;DR: In this article, the effects of nonplanar wing tip mounted surfaces on the lateral directional stability and control of low speed general aviation airplanes were studied, and good correlations exist between experimental data and theoretically predicted results.
Abstract: Nonplanar wing tip mounted lifting surfaces reduce lift induced drag substantially. Winglets, which are small, nearly vertical, winglike surfaces, are an example of these devices. To achieve reduction in lift induced drag, winglets produce significant side forces. Consequently, these surfaces can seriously affect airplane lateral directional aerodynamic characteristics. Therefore, the effects of nonplanar wing tip mounted surfaces on the lateral directional stability and control of low speed general aviation airplanes were studied. The study consists of a theoretical and an experimental, in flight investigation. The experimental investigation involves flight tests of winglets on an agricultural airplane. Results of these tests demonstrate the significant influence of winglets on airplane lateral directional aerodynamic characteristics. It is shown that good correlations exist between experimental data and theoretically predicted results. In addition, a lifting surface method was used to perform a parametric study of the effects of various winglet parameters on lateral directional stability derivatives of general aviation type wings.

Patent
14 Nov 1983
TL;DR: Auxiliary wing tips have a configuration which assure a wing surface continuity, especially when the tips are in their normal wing extending position, but also in any other position of the winglets as mentioned in this paper.
Abstract: Auxiliary winglets or control surfaces for aircraft wings are tiltable about an axis extending in the flight direction and about an axis extending substantially perpendicularly to the flight direction. The auxiliary wing tips have a configuration which assure a wing surface continuity, especially when the tips are in their normal wing extending position, but also in any other position of the winglets. Additionally, at least the leading auxiliary winglets are located upstream of the elastic wing axis, as viewed in the flight direction and they have a forward sweep or negative sweepback. The combination of these features permits a simultaneous reduction of induced drag and of stress caused by wind gusts, and for increasing the effectiveness of the wing's ailerons. Thus, these auxiliary winglets have three advantages simultaneously.

01 Sep 1983
TL;DR: In this article, a wing with fixed span which produces lift L, roll moment R, yaw moment Y and has minimal induced drag D is obtained by means of Prandtl's lifting line theory combined with computation.
Abstract: : Let L, R, Y be arbitrary real constants A wing with fixed span which produces lift L, roll moment R, yaw moment Y and which has minimal induced drag D is wanted This problem arises in airplane engineering It is solved by means of Prandtl's lifting line theory combined with computation (Author)

Proceedings ArticleDOI
01 Jan 1983
TL;DR: In this article, a Lissaman 7769 airfoil was tested in a low turbulence subsonic wind tunnel and lift and drag data were collected at chord Reynolds numbers at angles of attack from -10 to +20 deg by using an external strain gage force balance.
Abstract: A Lissaman 7769 airfoil, used on the Gossamer Condor and Gossamer Albatross human-powered aircraft, was tested in a low turbulence subsonic wind tunnel. Lift and drag data were collected at chord Reynolds numbers of 100,000, 150,000, 200,000, 250,000, and 300,000; at angles of attack from -10 to +20 deg by using an external strain gage force balance. Lift curves, drag curves, and drag polars were generated from both uncorrected data and data corrected for wind tunnel blockage effects. A flow visualization study was performed to correlate with the force data. The results of the investigation have shown that the airfoil exhibits a significant degradation in performance for chord Reynolds numbers below 150,000.

Proceedings ArticleDOI
01 Jan 1983
TL;DR: In this paper, a subcritical aerodynamic design computer code was developed, which used linearized aerodynamics along with sweep theory and airfoil data to obtain minimum total drag preliminary designs for multiple planform configurations.
Abstract: A subcritical aerodynamic design computer code has been developed, which uses linearized aerodynamics along with sweep theory and airfoil data to obtain minimum total drag preliminary designs for multiple planform configurations. These optimum designs consist of incidence distributions yielding minimum total drag at design values of Mach number and lift and pitching moment coefficients. Linear lofting is used between airfoil stations. Solutions for isolated transport wings have shown that the solution is unique, and that including profile drag effects decreases tip loading and incidence relative to values obtained for minimum induced drag solutions. Further, including effects of variation of profile drag with Reynolds number can cause appreciable changes in the optimal design for tapered wings. Example solutions are also discussed for multiple planform configurations.


24 Feb 1983
TL;DR: In this paper, the application of computational methods in aerodynamic design problems involving interference is discussed and a discussion is given on the problem of optimal usage of aerodynamic software in analyses and design, requiring an integrated systems approach.
Abstract: Examples are discussed of the application of computational methods in aerodynamic design problems involving interference. Amongst these are: subsonic wing-body, sting support, pylon-nacelle and pylon-store interference, high-lift devices, induced drag minimization through constrained optimization in the Treftz-plane and transonic wing-fuselage design and analysis. In addition a discussion is given on the problem of optimal usage of aerodynamic soft-ware in analyses and design, requiring an integrated systems approach.

Journal ArticleDOI
TL;DR: In this article, the effects of stream nonuniformity on the induced drag are found to be significant in a wide range of the parameters, including the velocity ratio and the scale ratio s/h.
Abstract: It is found that the effects of stream nonuniformity on the induced drag are significant in a wide range of the parameters. The variations of the drag factor k with the velocity ratio U0/Uj or Uj/U2 become stronger as the scale ratio s/h increases. For the jet and wake streams the effects are much larger than for the linearly sheared stream; this is due to the dependence of the solution for lift distribution on the second derivative of stream profile £/"(0), which was discussed in Ref. 1.

Proceedings ArticleDOI
01 Jan 1983
TL;DR: In this article, the progress of two studies which apply nonlinear aerodynamics to supersonic wing design is reviewed, and the results obtained during the course of these two studies are discussed.
Abstract: The progress of two studies which apply nonlinear aerodynamics to supersonic wing design is reviewed. The first study employed a nonlinear potential flow code to design wings for high lift and low drag due to lift by employing a controlled leading-edge expansion in which the crossflow accelerates to supercritical conditions and decelerates through a weak shock. The second study utilized a modified linearized theory code to explore the concept of using 'attainable' leading-edge thrust as a guide for selecting a wing leading-edge shape (planform and radius) for maintaining attached flow and maximizing leading-edge thrust. Experimental and theoretical results obtained during the course of these two studies are discussed.

Patent
06 Oct 1983
TL;DR: In this paper, the authors describe a rotating-wing aircraft, in which the wings rotate about themselves through an angle of 90 degrees of freedom (degrees of freedom) and the direction of the lifting force can be varied by displacing the point at which the drag of the wings changes.
Abstract: The invention relates to a rotating-wing aircraft, in which rotating wings (1) rotate about a horizontal axis (2), having high drag for downwards rotation and low drag for upwards rotation, so that a lifting force is produced counter to the force of gravity. The change in the drag is achieved in that the wings rotate about themselves through an angle of 90 DEG . The direction of the lifting force can be varied by displacing the point at which the drag of the wings changes.

01 Jan 1983
TL;DR: In swimming there has been a limited amount of research carried out investi­ gating the degree to which the forces generated by the upper limb contribute to the total forward propulsion of a swimmer.
Abstract: In swimming there has been a limited amount of research carried out investi­ gating the degree to which the forces generated by the upper limb contribute to the total forward propulsion of a swimmer (Schleihauf, 1979; Wood, 1979). Two types of forces are generated, induced forces and parasitic forces. Drag is a force component that is made up of both induced and parasitic forces, whereas lift is a force component primarily made up of induced forces.

01 Aug 1983
TL;DR: DRG program incorporates numerical optimization technique for calculating bound-circulation distribution required for minimum induced drag of nonplanar wings written in FORTRAN IV as discussed by the authors, which can be found in
Abstract: DRG program incorporates numerical optimization technique for calculating bound-circulation distribution required for minimum induced drag of nonplanar wings DRG written in FORTRAN IV

Proceedings ArticleDOI
01 Jan 1983
TL;DR: In this paper, the magnitude of the trim drag incurred by advanced supercritical wings and conventional wide-body wings at cruise conditions are investigated in a transonic pressure tunnel at a Mach number of 0.82 with a conventional widebody wing and supercritical wing with high aspect ratio.
Abstract: The magnitude of the trim drag incurred by advanced supercritical wings and conventional wide-body wings at cruise conditions are investigated. Experiments were performed in a transonic pressure tunnel at a Mach number of 0.82 with a conventional wide-body wing and supercritical wing with high aspect ratio (9.80) using one of three low-tail configurations or two T-tail configurations in order to determine the effects of horizontal tail size, location, camber and static margin. Drag measurements indicate trim drag for the supercritical wing not to be significantly higher than for the conventional wing, although the minimum drag values for the supercritical wing occurred at lower static margins than for conventional wings. Both wings exhibited a reduction in trim drag with reduced cambered tail size, and greater minimum drag increments for cambered tails than for symmetrical tails. Lower trim-drag increments were also observed for the T-tail configuration than the low tails. The increase in lift-drag ratio for the supercritical wing over the conventional wing amounted to 11% for the best tail configurations.


01 Jul 1983
TL;DR: In this paper, a 1/10th scale model of a BAe Jetstream was tested at the Cranfield Institute of Technology in the 8' x 6' low speed wind tunnel with sails and winglets, and the first objective of the tests was to demonstrate a measurable drag reduction for a Jetstream fitted with tip devices over the range of operational lift coefficients.
Abstract: : The formation of a strong tip vortex has an undesirable effect on the drag of a lifting surface. Firstly, it induces a strong downwash field locally which increases the vortex drag and secondly introduces a strong cross flow around the tip causing separation on the top surface. Tip devices seek to remove these effects. Sails unwind the tip vortex and in doing so experience a thrust, like stators behind a fan. Their nose to tail arrangement gives them the ability to carry high lift coefficients, in the manner of cascades or slotted aerofoils. Winglets, or tip fins attenuate the tip vortex by dissipating the shed vorticity along their length, thereby reducing the downwash induced at the wing tip region. In order to asses these effects, it was proposed that a 1/10th scale model of a BAe Jetstream (Figure 1) should be tested at Cranfield Institute of Technology in the 8' x 6' low speed wind tunnel with sails and winglets. The first objective of the tests was to demonstrate a measurable drag reduction for a Jetstream fitted with tip devices over the range of operational lift coefficients. The second objective was to estimate the increase in wing root bending moment due to either device in order to compare their relative merits with simple tip extensions. In the past this had been done with wing only half model with encouraging results, but an estimate for the complete aircraft configuration was highly desirable.

D. B. Benepe1
01 Feb 1983
TL;DR: A set of empirical methods was developed to predict low-speed lift, drag and pitching-moment variations with angle of attack for a class of low aspect ratio irregular plan-form wings suitable for application to advanced aerospace vehicles as mentioned in this paper.
Abstract: A set of empirical methods was developed to predict low-speed lift, drag and pitching-moment variations with angle of attack for a class of low aspect ratio irregular planform wings suitable for application to advanced aerospace vehicles. The data base, an extensive series of wind-tunnel tests accomplished by the Langley Research Center of the National Aeronautics and Space Administration, is summarized. The approaches used to analyze the wind tunnel data, the evaluation of previously existing methods, data correlation efforts, and the development of the selected methods are presented and discussed. A summary of the methods is also presented to document the equations, computational charts and design guides which have been programmed for digital computer solution. Comparisons of predictions and test data are presented which show that the new methods provide a significant improvement in capability for evaluating the landing characteristics of advanced aerospace vehicles during the preliminary design phase of the configuration development cycle.